The present invention relates to devices for actuating catheters.
Devices for actuating catheters are described in U.S. Pat. Nos. 6,391,051 B2; 6,375,676 B1; 6,238,402 B1; 6,146,415; 6,019,778; 5,201,757; and also in WO 00/10486 and DE 198 19 634 A1. The catheters described in these documents are to a major extent designed to be used for placing and splaying out in situ stents, such as stents for angioplasty, in particular stents of the self-expanding type. With a certain degree of simplification, but with substantial adherence to the actual situation, it may be stated that, in the solutions considered above, the relative movement designed to disengage the stent from the element or elements that the keep it in a radially contracted condition is left practically completely to the control of the operator. In particular, the speed for carrying the operation out is left to the control of the operator.
Clinical experience developed in the use of stents of this nature demonstrates, however, that this method is not altogether free from drawbacks. It is found, for example, that the action of splaying out the stent (performed gradually at one end of the stent and then involving the stent as a whole) must usually be performed in its initial steps in a delicate and gradual way. Precisely in these initial steps, the operator must, however, overcome quite a high initial force of friction, represented by the need to overcome the resistance opposed by the means of containment of the stent. Usually, these means of containment consist of a tubular tunic fitted on the stent that must be retracted by causing it to slide axially on the stent so as to uncover and gradually free the stent itself.
It may happen that the force applied by the operator in the initial step of the operation of splaying out, in a way commensurate with the need to start the movement of retraction of the tunic with respect to the stent, will be excessive in the subsequent steps of splaying out. All this entails possible adverse effects, above all when the stent in question is a stent for coronary angioplasty of small axial length, for example about ten millimetres. In the case of stents of a substantial axial length (for instance, certain peripheral stents), it may instead happen that the movement of disengagement of the tunic from the stent will end up being executed at an excessively slow speed.
There is a need in the art to provide a guide for the operator in carrying out the operation of splaying out the stent precisely by the device for actuating the catheter, thus preventing the criteria whereby the operation is carried out from being entrusted altogether to the operator. The present invention provides a device for actuating catheters that will be able to overcome the drawbacks referred to previously and to meet the aforesaid need to allow the criteria with which the operation is carried out to be left totally to the operator.
It will be appreciated that in the definition of the invention, reference is made herein to actuating catheters understood in a general sense. Even though the present invention has been developed with particular attention paid to its possible use for actuating catheters for the application of stents, and in particular self-expanding stents, it may be used to advantage together with catheters of any type in which it is in any case necessary, for use of the catheter, to perform a relative movement of parts of the catheter itself.
The invention will now be described, purely by way of non-limiting example, with reference to the annexed drawings.